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ADDRESS 



ON 



THE METRIC SYSTEM OF WEIGHTS 
AND MEASURES. 



BY 



BENJAMIN APTHORP GOULD. 



DELIVERED BEFORE 



The Commercial Club of Boston, 



February i8, 1888. 



AT ITS 184TH REGULAR MEETING. 



LIBRARY OF C0NGRE88 f 

RECEIVED 

47*121902. 

DIVISION OF DOCUMENTS. 



A^ 



n 



ON THE METRIC SYSTEM OF WEIGHTS AND 

MEASURES. 



Mr. President and Gentlemen: When you invited me to dine with 
3^ou to-day, and to address you upon some scientific topic, it was im- 
possible not to accept the flattering invitation, for I knew that it would 
enable me to meet again the gentlemen to whose great kindness I was 
indebted for that wonderful excursion of last June, the most charm- 
ing, instructive, and delightful that could be imagined, and the 
memor}^ of which will always be treasured. It is needless to say that 
I would not willingly lose any opportunity of expressing my gratitude. 

Unfortunately, my health, sadly shattered a couple of years ago, is 
not even yet so fully restored that it has been in my power to prepare 
my remarks with the care which ought to be devoted to an address in 
this presence. And not being able even to arrange their presentation 
in such form as I desired, I should have come with great hesitance 
had I not had good reason to know that I should be among friends 
who would be lenient to my shortcomings and gentle in their criticism. 

Having neither the gifts nor the training for a public speaker, it has 
been easier to write down what I have to say than to trust to the 
promptings of the moment. Therefore I have ventured to bring it in 
written form; and you will forgive it if my words lack that sparkling 
effervescence from the lips which you require of your genial beverage, 
but come to you laden with such flatness as belongs to ideas and 
expressions a day or two old. In return you shall have no statement 
which has not been weighed and tested at leisure. 

In selecting the subject it has seemed best for me to take one some- 
what outside the field to which my studies have been chiefly devoted, 
yet regarding which I have some right to speak, while it may probably 
have quite as much interest for you as would one less nearly connected 
with your daily pursuits and belonging to regions outside of our 
daily affairs. And so I propose to say something concerning the 
metric system of weights and measures and the steps taken toward 
perfecting it. Not to enter upon any advocacy of its adoption for 
exclusive use in this country, for that would be the renewal of a cru- 
sade which it is impossible that other and abler voices than mine 
should not undertake at no distant day, inasmuch as its extension and 
furtherance are closely connected with the progress of science and the 
arts, of the brotherhood of nations, and, in fact, of civilization itself, 
but to give some account of the introduction of the s}^stem, its develop- 
ment, and what is going on at present toward its improvement. 

In the year 1850 was published a remarkable and useful book by Mr. 
John H. Alexander, of Baltimore, entitled U A Universal Dictionary of 
Weights and Measures," and giving the values of standard weights 
and measures reduced to those of the United States. It contains 5,227 
weights and measures, with their equivalents. Leaving aside all which 

3 



4 METRIC SYSTEM OF WEIGHTS AND MEASURES. • 

are professedly distinct units. I had the curiosity to count the number 
of different kinds of pounds, feet, inches, pints, etc'. Taking, for ex- 
ample, the various sorts of inches, and using not only the English word 
"inch." hut the corresponding- words in other languages, pouce, Z<>Jh 
etc., 1 found 60. For foot, Fuss, pied, etc., there are 135. There are 
53 different distances called miles, and 29 sorts of pints, while for 
pound, Pfund, livre, etc., there are no less than 235! 

The utter confusion created by this uncertainty need not be described. 
Probably most of you, gentlemen, may have had some experience of 
it. although the introduction of the metric system throughout the 
European continent has already brought relief. But. until the recent 
unifications of Itah T , of Germany, and of the Austrian Empire, almost 
every petty state had its own measures, and these were changed by 
law from time to time. Even now, those of us who wish to know the 
value of various units in England lind plenty of trouble. If we are 
told that something weighs so many stone, or measures so many quar- 
ters, it requires a considerable amount of knowledge or experience to 
obtain the corresponding idea. 

The weight of a human being is generally given in stones of li 
pounds each; but for glass a stone is 5 pounds, for meat it is 8 pounds. 
In Scotland it varies, in different places, from 17 to 2'2, etc. Then. as 
to the sort of pounds, we must ask whether they are Troy pounds, 
and, if so, whether Scotch or English, or Tron. or the now customary 
avoirdupois pounds. A "quarter" may be the imperial quarter of 
about 8i bushels or the Winchester quarter of just 8 bushels: yet. 
when we come to bushels, there are some 40 different sorts — according 
as we may be measuring apples, or barley, or beans, or bran, or coal. 
or corn, or salt, etc. 

There was. and is. but one remedy for this condition of things: and 
yet it was not until the beginning of the French Revolution, a century 
ago, that any practical steps were seriously undertaken to bring about 
a cure. 

It was then proposed to enlist all civilized nations in a joint effort to 
create and adopt a new system, founded on some one unchanging natural 
unit as the standard of length. From the unit of linear measure, once 
established, it would be easy to derive those of surface measure and of 
volume. The measure of volume or bulk would, of course, supply 
that of capacity for solids or liquids, and that of weight or mass would 
then be afforded by that of a quantity of pure water, taken at the tem- 
perature of greatest density and corresponding to the unit of volume. 
It was further resolved that all the multiples and subdivisions of these 
units of length, area, volume, weight, should be decimal only, and 
that only these should be employed for all measurements of every 
sort and nature. The Arabic numerals, with their decimal notation, 
are among the very few things which are the same for all civilized 
mankind: and the decimal system which these imply was to be care- 
fully maintained for every dimension which they are employed to 
express. It is probable, too, that the American decimal currency, just 
then established, was an important agent in impressing our French 
allies with the extreme convenience of carrying through the affairs of 
daily life the same numerical system which is employed in express 
all abstract values. And yet another condition laid down was that 
each unit should receives name of its own, incapable of being confus^a 
with any other. 



METEIC SYSTEM OF WEIGHTS AND MEASURES. 5 

The ablest scientific men of France — men whose names are held 
to-day in as high reverence as during their lives, if not higher — warmly 
espoused this plan; and it was fully indorsed by the Paris Academy of 
Sciences. To secure the cooperation and assistance of other nations 
the National Assembly provided that all should be invited to join in 
the plan, and especially that the concurrence of Great Britain should 
be solicited. For some reason — probably the intense and reciprocal 
hostility of the two peoples, reenforced doubtless by that dislike of 
all change which is so characteristic of the English — this last provision 
was never carried into effect; yet, in the original consideration of the 
project, representatives from Spain, Italy, Netherlands, Denmark, and 
Switzerland took part. A committee had been appointed by the French 
Academy to decide upon the most appropriate natural standard. Vari- 
ous suggestions were considered, and it was finally decided to employ 
some one derived from the dimensions of our earth itself. And after 
long and mature deliberation the choice between the several standards 
was narrowed down to three — the length of the pendulum beating sec- 
onds in the forty-fifth degree of latitude, the length of the earth's cir- 
cumference at the equator, and the distance from the equator to the 
pole. Ultimately the last was selected; and it was resolved that the ten- 
millionth part of the quadrant of a meridian should form the basis of 
the new sj^stem and should be called a meter. This would be of con- 
venient size, intermediate between the man} 7 values of the ell, less than 
one-tenth longer than the yard, and, in fact, not very diverse from the 
accustomed units of linear measure in most civilized countries. Their 
report was made to the academy in March, 1791, approved and trans- 
mitted at once to the National Assembly, by which it was sanctioned 
and the needful provisions made for carrying it into effect. 

The new universal unit was to be deduced by an elaborate determi- 
nation of the length of the quadrant from equator to pole; and this 
was to be obtained by a geodetic triangulation, made with all possible 
precision, and over as long an arc of the meridian as possible. The 
work began at once, and the great undertaking of a measure of the 
meridian through the ten degrees from Dunkirk, at the northern 
extremity of France, to Barcelona, in Spain — a meridian which passes 
through Paris — was carried on for seven years under the direction 
of able and enthusiastic mathematicians and astronomers. In early 
life it was my privilege to occupy somewhat intimate relations with 
two of these men, Biot and Arago, then, of course, in advanced years; 
and it thrills me yet to remember their accounts of the privations and 
perils which they encountered in prosecuting the work during the ter- 
rible convulsions which distracted France through that period — mak- 
ing their observations in remote or dangerous regions, where the 
absence or presence of population were almost equally to be feared, 
and actually suffering capture and imprisonment. 

In the year 1799 the observations had been completed and the prin- 
cipal results computed; and an international commission, containing 
representatives of 10 independent States, was then convened at Paris 
to deduce and establish the precise length of the proposed meter. One 
midsummer day of that year the standard bar which represented the 
unit of length, and the standard kilogram for the unit of weight — both 
made of platinum — were formally deposited for safe-keeping in the 
Palais des Archives at Paris. Copies of the same, prepared with 
exceeding care, were also deposited at the Conservatory of Arts and 



6 METRIC SYSTEM OF WEIGHTS AND MEASURES. 

Trades, and at the observatory. These have been since then the stand- 
ards for the world, and with them have been minutely compared the 
standards constructed for the use of other countries. 

In selecting names for the various weights and measures resulting 
from the meter and its corresponding units, it was rightly deemed a 
matter of high importance that new words should be employed. And 
in deciding upon these, I can not think that the commission was fortu- 
nate. For although the nomenclature is very ingenious and elegant, 
it has an element about it which may easily pass for pedantry, and is 
ill adapted for employment in most modern languages. Indeed, this 
seems to have been at hrst the very greatest obstacle in the way of its 
adoption, even in France itself. The decimal multiples of the primary 
units are denoted by prefixes taken from the Greek; and the corre- 
sponding subdivisions, by prefixes derived from the Latin. Thus, 100 
meters are called a hectometer, while the hundredth part of a meter is 
a centimeter; a thousand grams make a kilogram, and the thousandth 
part of a gram is a milligram. For some European nations these words 
have been easily modified so as to conform to the spirit of their lan- 
guage; in others, and especially in English, this is not easy. 

The metric system is now the only legal system of weights and meas- 
ures for about 410,000,000 of people — the only prominent exceptions 
to its general use being in Russia, the United States, and Great Britain, 
in the last two of which, indeed, its use is authorized, although not 
generally adopted. 

I have described the origin of the system with some detail, both 
because it seems to me an important event in the history of civilization, 
and because sundry criticisms, emanating from some of our ultra- 
conservative kindred on the other side of the water, have tended to 
create erroneous impressions. It has been spoken of as a French, and 
not a cosmopolitan institution: whereas in truth no efforts were spared 
by its authors to give it a thoroughly international character, so far 
as possible. Various nations were associated with its origin, a still 
larger number with its definite establishment, and now its adoption by 
a vast preponderance of the civilized nations has removed every pos- 
sible tinge of localism and made it absolutely cosmopolitan, with the 
one possible but not necessary exception of its nomenclature. Then. 
it has been said that the value obtained was not correct : that the adopted 
value is now known not to be exactly the ten-millionth part of a quad- 
rant. To this it may be replied that the objection is frivolous: that it 
matters not in the .slightest whether the adopted value were absolutely 
correct or not; that the adopted standard is a certain bar of metal at 
a certain temperature, aiming to represent an ideal value, and that 
any small deviation from such value is of absolutely no consequence. 
But let me tell you just how much foundation that criticism has. 
whether important or not. 

It will not and never could In 1 supposed that the progress of science 
and the arts in a century would not permit the methods of observation 
oi" the instruments employed to be so improved that a repetition of 
the original investigation would not give slightly different and doubt- 
less more accurate results. Unimportant but real differences would 
unquestionably be found whenever the measures should be repeated. 
This has. however, not been done, nor is there any reason to suspect 
inaccuracy in the former determination, other than the imperfection 
which belongs to all work of men's hands. For that epoch the results 



METEIC SYSTEM OF WEIGHTS AND MEASURES. 7 

seem to have been uiarvelously accurate. But since then similar 
triangulations and measurements have been made in many countries — 
Russia, India, South Africa, the United States, Chile, and elsewhere — 
and they have brought to light the unexpected fact that the earth is 
probably not a regular spheroid; for the distance by which its polar axis 
is shorter than the equatorial is given differently by each successive 
measurement in a new region, and indeed by different parts of the same 
measurement, the results varying by comparatively large amounts; 
and the inference is nearly irresistible that our earth is not accurately 
a spheroid of rotation, but that its equatorial diameter varies in different 
longitudes. Thus, the length of a quadrant in one meridian is differ- 
ent from that in another meridian. Possibly the meter may differ 
from its intended value — the ten-millionth part of the quadrant which 
passes through Paris — by about the two-hundredth part of an inch; and 
yet the same results concerning the true figure of the earth, which give 
that inference, make the meter to be almost precisely the ten-millionth 
part of a quadrant of the meridian passing through New York— differ- 
ing in fact from this hj less than the ten-thousandth part of an inch. 
This would make the actual quadrant for New York to differ from 
10,000,000 meters by about 80 feet. So that were the objection of any 
importance, it could be readily disposed of by a slight change of defi- 
nition, putting the word New York instead of Paris. It might be, 
also, by a modification of the temperature at which the length of the 
bar is to hold good. 

But all these considerations are practically unessential. The prac- 
tical end in view was to secure some definite and material standard of 
length, upon which all nations should agree. It was evidently desira- 
ble that this should be derived from some natural dimension; and 
since, owing to the want of absolute precision in any work of human 
hands, it can not be expected that any degree of accuracy should be 
attained which may not subsequently be surpassed, it suffices amply 
that a near approximation be reached. Each successive future deter- 
mination will give a slight^ different value; and this state of things 
will continue so long as the earth itself lasts, and would be just as 
true of any other natural standard as of this. 

The new system was forced upon the French people by compulsory 
legislation, and without giving them proper instruction as to its nature 
and peculiar features. Naturally it aroused opposition, for the new 
units required a violation of their confirmed habits and prejudices; 
yet a very few years sufficed to make them not merely familiar with 
but cordiall} 7 attached to it. The same is true, in a yet higher degree, 
of those countries into which it was soon carried by the conquests of 
the Empire; for it was a constant reminder of their subjugation, and 
it was repudiated by most of them on their emancipation from the 
French yoke. Yet, notwithstanding these obstacles to its resumption, 
its excellencies are such as to have brought about since then its volun- 
tary adoption by them all. 

The consolidation of different states requires a unification of their 
weights and measures; and, in agreeing upon a new system, the}^ nat- 
urally desired to select the best. And, furthermore, one which should 
be in common with other nations would, even if a poor one, be evi- 
dently preferable to any other which had only a local application. 
Statesmen needed it for their custom-houses, and it has already done 
much toward abolishing frontiers; scientific investigators, who form 



8 METRIC SYSTEM OF WEIGHTS AND MEASURES. 

but a veiy small class in any one county, needed it for their common 
researches and the comparison of their results; artists needed it for 
analogous reasons; so, too, did medical men, whose experience ought 
to be shared b} T their colleagues of all nations; artisans and mechanics, 
those whose products were to be exported to other lands, as well as 
those who imported from outside their own boundaries; commercial 
men, who might thus avoid troublesome conversion of their invoice 
values; engineers in different lands, who could escape petty and vex- 
atious changes of dimensions to make their results niutualty compara- 
ble, and so on. 

To-day the only states of continental Europe in which the metric 
system is not fully established as the only legal one are Russia, 
Sweden, Denmark, and Turkey. Even in these it is permissive in all 
but Denmark and Russia; in Sweden it goes into operation next Jan- 
uary, while the Danish system is based upon metric values, so as to 
be easily convertible into them. On our own continent, it has been 
adopted as the one legal system by Mexico, Brazil, and almost all of 
the South American Republics. In short there is a total of more than 
400,000,000 people thoroughly committed to the metric system, besides 
the hundred and twenty -two millions for whom it is permissive. 
There remain no civilized nations of any importance, excepting Russia 
and Japan. When the system shall have been fully adopted in our 
own country, as I firmly believe it will before many years, none ex- 
cept these two and England will remain outside, if indeed they do. 
For all three of them are already members of the international metric 
league, of which I am to tell }"ou, and all contribute annually to its 
support. 

It scarcely needs especial mention to remind you that the import- 
ance of the highest accuracy and extreme care in the preservation and 
verification of the standards of measure and of weight is quite as 
decided from a scientific as from a commercial point of view. In the 
delicate researches of physics and chemical science, which deal with 
quantities far below the reach of our microscopes, this precision is no 
less but indeed far more requisite than in the explorations of the astrono- 
mer. The relative atomic weights, the structure of crystals, the dimen- 
sions of the various waves of light, the expansion of bodies by heat, the 
units of force, and numberless other subjects of research demand not only 
the highest precision attainable, but likewise a uniformity of the stand- 
ards employed by different investigators. Not only is the number of 
explorers of nature's laws very small, but they are distributed through 
many countries and working under varied conditions. If their 
researches are to result in the greatest common progress, their stand- 
ards of dimension must be identical, or very easily converted. Geodetic 
investigations, too, must be comparable with one another, as well as 
those in physics and in chemistry. 

For this reason it has long been the custom for physicists and chemists 
of all lands to conduct their researches in metric units. And there 
would be little danger of error in saying that more than nine-tenths of 
the chemists of the world and three-fourths of all the physicists — 
English. American, and Russian, as well as others — employ exclusively 
the meter and the gram. Vet what security has there been that the 
standards for even these units, existing in different countries, were 
practically identical \ 

The need of securing actual, as well as nominal, uniformity in the 



METRIC SYSTEM OF WEIGHTS AND MEASURES. r , 9 



£«&* 



units employed had been making itself felt more and more through a 
series of years, until in 1868, the Government of France, at the 
instance of the European Geodetic Association, issued a circular to all 
the nations with which it was in diplomatic relations, inviting them to 
appoint delegates to a conference at Paris in 1870, in order to adopt 
measures for securing permanence and uniformity in the various 
standards of weights and measures, and to devise means of reproducing 
these standards with all possible accuracy. 

Agreeable to this invitation the delegates of 21 nations, represent- 
ing the majority of civilized human beings, assembled in Paris on 
the 8th of August, 1870. The time proved most unfortunate. War had 
been declared less than three weeks before, the representatives of 
Prussia and England were absent, and the condition of affairs was as 
unfavorable as could well be for scientific thought or deliberation. 

Still some action was had in agreeing upon certain general principles 
which might be followed. And it was resolved that measures should 
be taken for extending the international character of the metric sj T s- 
tem, but without undertaking any modification of the existing value 
of the meter. Various ends to be attained were clearly defined. A 
commission representing 30 nations and containing some of the most 
eminent scientists of Europe was appointed to make the preliminary 
experiments and investigations, and definite principles were laid down 
to guide them. Among the duties with which they were charged was 
that of making a careful study of the properties of such materials as 
might appear to be suitable for the construction of the new standards, 
and into the best forms and modes of construction. The French Gov- 
ernment promised its full support to all the decisions of the conference, 
which then adjourned until some more auspicious time. 

During the session of this conference its members had made a formal 
visit to the bureau of archives in order to inspect the platinum standards 
there deposited. These had been found in excellent condition; and 
among the rules recommended was one to the effect that as man}' copies 
of them should be made as there were nations represented, and with all 
the precision which the resources of science and the arts would permit; 
that one of these be selected as an international prototype for all future 
time and preserved with every precaution, while the others should be 
distributed among the participating countries; also that an analogous 
course should be pursued with reference to the standard kilogram. 

The need of such precautions as these had been signally illustrated 
during the year following this conference. At the same time that the 
Tuileries were burned by the commune orders had been given to 
destroy the archives of France simultaneously with the other public 
buildings and the column of the Place Vendome. It was only through 
an accident that the plan failed; but in the meanwhile two of the 
members of the commission had secretly abstracted the standard meter 
and kilogram from their place of sacred deposit, and had hidden them 
elsewhere, inclosing a statement of the hiding-place in a sealed letter, 
deposited with the Academy of Sciences. 

The international commission distributed the subjects referred to it 
among ten subcommittees; and two years later, in the autumn of 1872, 
it reassembled at Paris for definite action. A full plan of operations 
and a most elaborate code of recommendations for their execution 
were then agreed upon, as well as a resolution asking the French Gov- 
ernment to invite another international conference for the purpose of 



10 METRIC SYSTEM OF WEIGHTS AND MEASURES. 

acting on these recommendations and of considering the establishment 
of an international bureau to take charge not merely of the construc- 
tion of the new prototypes, but also of the preservation of the inter- 
national standards, and their periodical comparison with those proto- 
types, which were to be distributed among the several nations, and 
with such other fundamental standards as have been or are to be used 
for geodetic or other important operations. 

On the 1st of March, 1875, the new conference was held, consisting 
of the representatives of twenty -one nations; England only having 
declined out of all those invited. 

The commission presented its results, and an international league 
was formed by an agreement in the nature of a treaty under the name 
of the '"metric convention." By this compact, which has now been 
in practical operation for nearly twelve years, the several constituent 
nations agreed to maintain, at their joint expense, an international 
bureau of weights and measures at Paris. This was to be conducted 
under the exclusive direction and control of a so-called "international 
committee," subject in its turn to the authority of a "general con- 
ference of weights and measures," a body of diplomatic character and 
composed of delegates appointed by and representing all the contract- 
ing powers. 

It was provided that the international committee should be composed 
of fourteen members, each belonodnof to a different nationality and 
charged with the duties of superintending the new prototypes, of veri 
f} T ing them when completed, of preserving the international -ones, of 
superintending such other operations of the sort as might be under- 
taken by the nations in common, of making periodical comparisons of 
the standards distributed to the different nations, of verifying, and 
comparing the measures which have been or might be employed in 
geodetic operations, etc. (not only for governments but for scientilic 
institutions), of providing the requisite apparatus, etc. 

The bureau of the establishment was to be established at Paris, in 
some building to be specially prepared or constructed by the committee, 
and the French Government to give it legal immunities. 

The contributions of each nation were to depend upon its population 
and upon the employment which it makes of the metric system, 
whether it is obligator}', or permissive, or neither. 

And, finally, it was provided that the deliberations and votes of the 
committee might take place by correspondence, excepting that one 
session be held annually, up to the time of the completion of the pro- 
totypes, and one in each two years thereafter; the conference itself 
(the diplomatic body) to be convened when the prototypes were ready 
and afterwards at the call of the committee, as often, at least, as once 
in every six years. 

Such is the metric convention, now composed of all the principal 
nations of the civilized world excepting Holland and Brazil, in both 
of which countries, however, the metric system exclusively prevails 
for legal use. but which other considerations have hitherto prevented 
from definitely joining the league. In the unanimous report of a com- 
mittee of the American Association for the Advancement of Science, 
among whose eight members were President Barnard of New York. 
Professors Henry of Washington. Rogers of Boston, and Peirce of 
Cambridge, this international league was declared to bo "more honor- 
able to civilization than almost any other that was ever entered into 
by such high contracting parties." 



METRIC SYSTEM OF WEIGHTS AND MEASURES. 11 

The international committee entered at once upon its duties, begin- 
ning in April, 1875. After careful examination and deliberation they 
selected an edifice of some historic interest, known as the Pavilion de 
Breteuil, situated near the entrance of the Pare de St. Cloud, not more 
than a gunshot from the celebrated porcelain factory of Sevres, which 
it overlooks. The French Government has given the use of the land 
and building, and declared it international territory so long as it shall 
be devoted to its present purpose. Here have been built the work- 
shops, laboratories, and the subterranean vaults for depositing the 
standards; and here go on the experiments and researches of every 
kind. 

The platinum Metre des Archives was established as the standard to 
which the new ones must be made to conform with all possible accu- 
racy- This has been found to differ slightly from the platinum Metre 
eki Conservatoire, not only in its coefficient of expansion — that is to 
say, the amount of its increase of length for the same increase of tem- 
perature — but also in its actual length at the standard temperature, at 
which the difference amounts to nearly four-thousandths of a milli- 
meter — that is, to about the sixt} r -two hundredth part of an inch. The 
different value of the constants of expansion for the two bars can only 
be accounted for hj some difference of chemical constitution or of 
density, notwithstanding that the} 7 were constructed by the same 
maker and at the same time. Probably they were cast at different 
meltino-s. 

In preparing the new standards it was the firm resolve of the inter- 
national committee that no source of error or uncertainty should be 
left which human knowledge or skill could avoid. To escape all danger 
of any modification by atmospheric influences by molecular change or 
b} 7 use, it was requisite that the material should be the most refractory 
and hardest attainable, absolutely homogeneous, and of the highest 
purity. After many experiments and much study it had been decided 
by the commission of 1872 that an alloy of platinum and iridium should 
be emplo3 r ed, combined in the proportions of 9 to 1, with a tolerance of 
not more than 2 per cent in the proportion of either, and that especial 
care should be taken to avoid the smallest intermixture of an} 7 one of 
the three metals which would most endanger its permanency, whether 
as regards extremes of temperature, or atmospheric influences, or 
molecular changes. These three metals, which are almost always found 
combined in small quantities with platinum and iridium, and are pecu- 
liarly difficult to remove b} T chemical processes, are iron, ruthenium, 
and osmium; the alloy of the last with iridium being what we all 
know in the nibs of our gold pens. 

The preliminaiy preparations having been concluded, and the con- 
stituent metals obtained and purified, the melting was first essayed on a 
small scale; and these results appearing satisfactoiy, the casting of a 
large mass took place with great state. The work had been intrusted 
to the French members of the original commission — members of the 
Academy of Sciences, and of a world-wide reputation. A large cruci- 
ble of chalkstone had been made and special furnaces, heated by huge 
ox} 7 hydrogen flames, constructed. The President of the Republic and 
the minister of public instruction were present and a number of the 
members of the Academy of Sciences. The heat produced was so 
intense that in a few minutes the metals — among the most difficult to 
melt of any known— were converted into a glowing mass as brilliant 
as the sun. This was poured into the chalk mold to form the ingot, 



12 METEIC SYSTEM OF WEIGHTS AND MEASURES. 

which was not far from 44 inches long, 7 wide, and 3 thick, if I may 
venture to name its dimensions in such vulgar units. It weighed about 
200 kilograms, or. say, 440 pounds. When it was exhibited to the 
Academy of Sciences four men were needed to carry the tray on which 
it rested; yet had it been an ingot of aluminum of the same size it 
would have been easy for any of us to hold it out at arm's length. 

From this a kilogram weight was prepared and furnished to the 
international committee for its preliminary study; but, to the dismay 
of all. the impurities, especially the metal ruthenium, were found by 
them to surpass the limit of tolerance prescribed, being about 2% per 
cent instead of 2 per cent. The whole mass of material had to be 
rejected, a proceeding not at all acceptable to the gentlemen under 
whose direction it had been prepared. The}* declared it impossible to 
obtain greater purity, professed to regard the committee's action as an 
indignity to their nation, and the discord threatened at one time seri- 
ously to imperil the existence of the international committee. But 
one of its members, M. Stas, of Brussels, with the aid of that gifted 
French chemist, the late H. St. Clair Deville, took up the problem; 
and within less than two years the}* had devised and carried out a new 
process, by the aid of which it has been possible to obtain material 
almost pure, the amount of impurities of every kind in the material 
finally employed being less than one-fourth of 1 per cent, or amounting* 
to only about one-tenth of the tolerance which had been originally fixed 
as the limit. It took seven years to attain this end, but it has been 
attained. 

Then came the question of form. For the kilogram standards this 
was easy to decide. The weights are nearly cylindrical, having a 
diameter equal to the height, while the edges above and below are 
rounded to avoid angles. But for the meter bars this question was 
serious. The temperature at which the measurements are made is a 
very important element; and although the surface temperature of the 
bars may be easy to determine, it is very difficult, if not impossible, to 
know how far that temperature is uniform throughout the mass. To 
be sure, the standards are kept for some hours previous to use in the 
same circumstances of position and temperature in which the compari- 
sons are to be made — generally in a bath of glycerin, maintained at a 
fixed and uniform temperature by especial precautions. Still, there is 
always a possibility that there may be som? difference of tempera- 
ture between the interior and the surface; and so the form given to 
the meter bars is such that their cross section is nearly in the shape of 
an X, the narrow plane on which the divisions are traced being at the 
upper angle and just in the middle line of the bars. 

The question of support has been a serious one. lest there be any 
tendency to bend; but more troublesome still has been that of the 
polish of the surface on which the divisions are traced. These divi- 
sions are read by microscopes; and the mode of illumination is neces- 
sarily different for a dead polish and for a bright specular one. Of 
course, the mode of tracing the divisions, their depth and shape, have 
received careful study; and there seems to be left no opportunity for 
reasonable doubt as to the completeness of every precaution. The 
international standard is to be deposited in the subterranean vault. 
upon a carriage specially devised, and accompanied by three others. 
each of which has been minutely compared with it; and the whole. 
together with the kilogram standards, closed with three locks, one key 



METEIC SYSTEM OF WEIGHTS AND MEASURES. 13 

being in the custody of the president of the international committee, 
one in that of the director of the bureau, and one in that of the 
director of the French bureau of archives. Thus there will be no 
possible access to it, except by the concurrence of these three officials, 
and not even for the director of the bureau, except by a vote of the 
international committee and in presence of two of its members. 

The kilogram standards are now completed. The old standards of 
the Archives and the Observatory were also found to differ from one 
another by an amount perceptible with the new balances. The former 
was adopted as the standard; but, although its weight wi 7 l be extremely 
close to that of a cubic centimeter of pure water at the temperature of 
greatest density, the case is like that of the length of the meter already 
spoken of; and its deviation from the absolute theoretical value will 
doubtless become more and more appreciable with the advance of arts 
and sciences. At present it is not surely known whether it is in 
excess or defect; but the researches now making at the bureau of the 
international committee will doubtless solve that question before long. 
The temperature of greatest density for water is first to be fixed. 
This is only known at present to within a fraction of a degree of the 
centigrade scale. A department of thermometry has been recently 
established at Breteuil, and investigations have been making which 
will greatly add to the precision with which temperatures can be deter- 
mined. Various sources of error have been discovered, to which 
the best thermometers are subject, apart from possible want of uni- 
formity of the caliber of different parts of the tube. It has been found 
that the chemical composition of the glass emplo} T ed exerts a very 
decided effect, owing to the consequent difference in the relative expan- 
sion of the glass and the mercury. 

The most delicate and accurate thermometer that has thus far been 
made is one which employs pure lrydrogen gas instead of mercury; 
and this has been adopted as the standard thermometer, by whose indi- 
cations all others are tested. Also the coefficients of expansion for the 
material of the standards, as well as for pure mercury, to say nothing* 
of the various sorts of glass used, have been determined with a precision 
never before attained, whether we consider the methods employed or 
the minute and punctilious care with which the work is prosecuted. 

In short, it has been the aim of the committee to be satisfied with 
no results of any sort not in advance of what the world had previously 
attained. Composed of representatives of fourteen different nations, 
it has been hoped that their joint efforts would lead to results beyond 
what could be expected from any one man; and it ma}^ fairly be 
claimed that up to the present time no one of the various arts or 
sciences whose aid has been required has failed to receive a decided 
and important impulse from the demands made upon it by the Inter- 
national Bureau. The new and wonderfully delicate apparatus for 
graduating the bars, for comparing the finished standards, for preserv- 
ing uniformity of temperature, for determining the coefficients of 
expansion, for calibrating thermometer tubes, the balances for weigh- 
ing heavy objects in vacuum and in water, the chemical processes for 
purifying the metals, the mode of fusing them, and the mechanical 
processes for fashioning them, the exquisite form and evenness of the 
divisions, traced upon metal of more than adamantine hardness, no less 
than the accuracy of the graduation itself — these represent but a part 
of the man}^ advances due to the International Bureau; and it is 



14 METRIC SYSTEM OF WEIGHTS AND MEASURES. 

scarcely too much to say that in every one of these directions progress 
has been made 4 to an extent unknown, if indeed considered possible, 
a do/en years ago. 

Let me give one little illustration. In L880 a certain number of the 
kilograms had been completed, and it was necessary to determine the 
discordances of each from the old standard, preserved in the French 
archives, and to which the new international standard was to be made 
as closely approximate as possible. Four of them were thus com- 
pared, and all found very close to the original. One of them seemed 
a little nearer than the others, and differing. indeed, almost impercepti- 
bly from the standard, yet certainly a little heavier. Its material was. 
of course, this so-called platin-iridium, so hard that a diamond point 
marked it with difficulty, and so heavy that when put into mercury 
it would fall to the bottom with a splash like that of a stone in a pail 
of water. Professor Stas. the eminent chemist who represents Bel- 
gium in the committee, undertook the task of bringing it still more 
closely into conformitv. and succeeded in doing- so by taking the weight 
into his hands, clad in white kid gloves, and rubbing it with his fore- 
finger. Since then it has been impossible to ascertain which of the 
two is the heavier at the standard temperature. Raising or lowering 
the temperature a very little, the difference due to the slight differ- 
ence in the changes of their bulk thus produced becomes perceptible, 
for the buoyancy of the surrounding air or water is thus made appre- 
ciable; but when weighed in a vacuum their weights are sensibly equal 
at all temperatures. 

Weighed in air of the adopted temperature and barometric pressure, 
the index of the balance, which of course is inclosed in glass, will he 
seen to rise on that side which the observer approaches most nearly. 
Some curious and rather disturbing experiences have made this fact 
altogether too palpable. 

The particular piece of metal of which I speak has now been 
adopted by the committee to be the international prototype of the kil- 
ogram; and w r hen the decision of the committee shall have been 
approved by the diplomatic conference, which will be summoned for 
the purpose so soon as the national prototypes are ready for distribu- 
tion, this will be the only standard for the world, superseding all others 
for legal purposes, even in France, where the orignal one from which 
this was derived will cease to have other value rhan the historic. 

It will readily be seen that all this work has taken time. Nine years 
passed after the organization of the International Committee before 
the material for the standards was obtained with satisfactory purity 
and in sufficient quantity, and many of the delays have been most 
vexatious. Bui there is every reason to believe that in the course of 
another year all the standards of weight and measure bespoken by the 
several constituent nations, as weH as the international prototypes of 
length and weight, together with the three subsidiary ones which are 

to authenticate each of these, will be completed. The diplomatic con- 
ference will then be convened to eon t inn the acts of the committee, the 

national prototypes will be dist ributed. and the second stage of the 

committee's labor-- will begin. 

Had I not already occupied so much o\' your time, there are one or 
two other points which might perhaps have some interest for you. 
Such, for instance, is the mode of measuring with the meter bars, the 
end- of which were formerly used, but which can not well be employed 



METRIC SYSTEM OF WEIGHTS AND MEASURES. 15 

with sufficient precision in this way, the length being now given by 
the distance between two lines, traced near the extremities and observed 
with microscopes. Such, too, is the difficulty which has been found 
in placing distinctive marks upon the several weights without impair- 
ing their accuracy, since any cavity made by a graving tool invites 
dust. And so on. But I will mention one matter more. 

In the search for natural standards it was found out of the question 
to find one which could be easily redetermined; but that difficulty 
seems now to have disappeared. The discoveries of recent years have 
afforded means for measuring with great precision the dimensions of 
the waves of light of any color; and this, which was once only a theo- 
retical, ideal unit, promises now to be the most trustworthy and easily 
determinable of all. The International Committee will probably at no 
distant time determine these dimensions in metric units for rays of 
several different colors, and thus provide a new definition for the 
adopted standard. 

It may be worth mentioning to you that all the members of the 
International Committee serve in that capacity without remuneration, 
except that most of the governments refund to their representatives 
their necessary traveling expenses in attending the sessions. 

In concluding, let me read a short passage from the report of the 
committee of the American Association for the Advancement of 
Science, to which I have already alluded. They say — 

It is to be considered that this organization is not designed merely to advance the 
interests of the metric system of weights and measures, or to serve as a means of pro- 
moting the extension of that system. Its design is higher than that. To secure the 
universal adoption of the metric system would be, undoubtedly, to confer an immense 
and incalculable benefit upon the human race; «but it would be a benefit felt mainly in 
the increased facilities which it would afford to commerce, and to exactness in mat- 
ters that concern the practical life of humanity. But to secure that severe accuracy 
in standards of measurement which transcends all the wants of ordinary business 
affairs, yet which in the present advanced state of science is the absolutely indis- 
pensable condition of higher progress, is an object of interest to the investigators of 
nature immensely superior to anything which contemplates only the increase of the 
wealth of nations. 

This International Bureau proposes now to provide for science precisely that which 
science in the present age of the world demands — such minute exactness of measure- 
ment that observations of the most delicate character which may be made in Ger- 
many or Italy or France or England may be exactly and quantitatively known to 
the investigator in the United States who reads the measures as they are set down 
in the journals and the memoirs in which the original observations are described. 
It is of secondary consequence whether the standards are metric standards or standards 
which are in use among ourselves. This bureau will equally verify them all and 
compare them all with standards of other nations founded on different linear bases, 
so long as such differences shall continue to exist. It is therefore not merely an 
International Bureau of Weights and Measures, but it may with equal propriety be 
called an international bureau for the promotion of exactness in scientific determina- 
tions; and it will be as much the organ of institutions like this association, like the 
National Academy, like the Royal Society, like the French Institute, etc., as it wi " 
be that of the governments establishing it. 

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